Pump



July 13, 1948. H. MOLLY 2,445,232

PUMP

Filed Jan. 7, 1939 w/ya;

, driving member.

Patented July 13, 1948 PUMP Hans Molly, Berlin-Tempelhof, Germany;vested in the Attorney'General of the United States Application January7, 1939, Serial No. 249,805

In Germany January 5, 1938 Sections 1 Claim. 1

. This invention relates to improvements in or relating to hydraulicallyoperating transmitting devices of the piston type, comprising a cylinderblock having several cylinder bores, said block being rotatably mountedaround its longitudinal axis, and a driving member whose axis ofrotation may be inclined to the longitudinal axis of the cylinder blockfor changing the piston stroke. The piston rods of the pistonreciprocating in said cylinder block are hinged to said driving member.

The well known devices of this type are usually provided with a Cardanjoint for driving the cylinder block from the driving member. In

some cases the Cardan joint is arranged to simulembodiment the playbetween the piston and piston rod is limited to the kineticallynecessary freedom of movement and this freedom of movement is restrictedas much as possible, the piston rods will already afford a centeringbetween the cylinder block and driving flange in the driving flangeplane, i. e., a centering with respect the center of the effectivedriving plane.

The primary object of the invention is to provide a special centeringmember for positively guiding said driving member and said cylinderblock with respgct to one another concentrically to the centre of theeffective driving plane. This centre is to be defined as the centre inwhich the driving member axis intersects the plane comprising the hingepoints of the piston rods to the In this way the advantage is obtainedthat in gears inwhich the inclination between the cylinder block axisand the driving flange axis is variable in relation to the variations ofthe stroke, small deviations of the axis of inclination from theeffective driving flange plane are permissible which is very desirablewith respect to difficulties of mounting and displacements by forces. Itis further of essential importance that on account of this arrangementno further support of the cylinder block in the tilting frame isnecessary beyond its fixation by means of the controllingsurfaces.

A further object of the invention is to overcome the difiicultiesencountered in cases in which said special centering member is providedand at 3 and 10, Public Law 690, August 8, 1946 Patent expires January5, 1958 2 the same time the piston rods are hinged to the drivingmember.

Furthermore the invention aims to improve the means for hydraulicallyrelieving the controlling mirror face cooperating with the end face ofthe cylinder block.

Other objects, aims and advantages of the invention will be more fullyexplained in the following description with reference to theaccompanying drawing in which:

Fig. 1 is a sectional view of the transmitting device according to oneembodiment of the invention.

Fig. 2 is a sectional view of the transmitting device according toanother embodiment, in which the controlling mirror face and the endface of the cylinder block are spherically formed.

Fig. 3 is a plane view of the control orifices of the rotating cylinderblock of Fig. 1.

. Referring now to the drawing Fig. 1 illustrates the wellknowntransmitting device of the piston type, comprising a cylinder block Ihaving several cylinder bores 3 arranged around the axis of rotation 2.4 is a piston provided in each of said bores 3, the piston rod 4a beinghinged at its outer end to a driving disc or flange 6 by means of a ball5. The axis of rotation I of the driving disc 6 may be inclined relativeto the cylinder block I as shown in Fig. 2. For this purpose thecylinder block I is swingably mounted around an axis 8 passing throughthe point of intersection of the two axes 2 and I mentioned above.Therefore, the axis 8 lies in the plane comprising the centre of theballs 5. 9 is a frame mounted for angular adjustment around the axis 8,said frame being shown to have a controlling mirror face In which is inengaging relation with the end face of the cylinder block I so as tocontrol in a wellknown manner the communication of the cylinder bores 3with the input and the output channels II and [2 respectively.

In the embodiment shown in Fig. 1 these two channels lead to the pivotaxis 8. The special centering member for auxiliary centering of thedriving disc or flange 8 and the cyllnderblock l with respect to oneanother is shown tobe a ball l3 whose centre coincides with the centreof the effective driving disc plane, i. e., the point of intersection ofthe two axes 1 and 8.

According to Fig. 1, the ball I3 is arranged on the cylinder block I,whilst the supplemental ball cup I' l surrounding said ball 13 ismounted on the driving discor flange 6. The ball I3 is guided inacentric bore I5 of the cylinder block I and 3 is kept in engagingrelation in said cup hi by means of a spring it.

Of course the ball and its cup may be exchanged, i, e., the ball may bearranged on the drivingdisc or flange ti and the cup on the cylinderblock Land thus it is possible'to fixedly-arrange the ball to thedriving disc. In the reversed arrangement according to Fig. 1 careshould be taken that in spite of any deviations of the pivot axis 8 fromthe effective driving disc plane the centre points of theballs remain inthis plane. For this reason the bail-13 isarrange'd axially displaceableon the cylinder block- I -as shown in Fig. 1. As will be seen, the balll3-may displace itself in said bore l5. On the other hand by means ofthe spring it the'end face 'of the cylinder block i' is always heldin-contactwith the controlling mirror face iii. In this respect it is tobe noted that the cylinder block may be displaced in its longitudinaldirection .in order to guarantee the engagement of or contact withithecontrolling mirror surface and to rerid'erineffec- 'tive'any deviationsof the pivot axist 'fr'om'the effective driving disc plane.

' From the foregoing it follows thatthe cylinder block I is guided onlyby means of the" centering ball l3, its "end face engagingtheicontrolling mirror face [0. This is of 'importance'in iview of'thefactthat it is practically impossible to avoid difficulties in the eventthat the cylinder block is'positively guided in the swingableframe'Qasisusual. According to the inventionythe said guiding of the cylinderblock l at its frameil "results'fromthe contact of its end face on thecontrolling mirror face so'thatthe' danger of clamping of the cylinderblock is avoided.

The embodiment shown in 'Fig. '2 differs from that shown in Fig. 1therein thatlthe controlling mirror facelo'has a spherical'shape'instead of th customary plane shape. In order to explain the advantagesobtained by this" feature in'ithe following the forces existing at'thecylinderblock end face are considered as compared with Fig. 1:

' 'These forces are:

l 1. "The force" PkWhi Ch is caused by the pistons. "2. The force'Pswhich results fromthe'de'livery pressure existing'in the controllingslit H.

"In' order that th cylinder block I continues 'toiengage' thecontrolling mirror the force'Pe (with the larger'lever arm a) mustbegreater itnan the'force'Ps (with the sm'aller'lever arm'b) 'The'magnitude-of the force'Ps now depends to a high "degree on how thepressure between the tightening surfaces of th controlling mirror H] and-the cylinder block l'decreases around the controlling slit, "Due tothis the forcePs is not predetermined so that an auxiliary force Pr iscreated by hydraulical means for the purpose of compensatingfluctuations of the force Ps. The force Pr is generally thus created inview of the fact that an equilibrium chamber 19 is provided in thecylinder block. The pressure in this chamber is controlled in dependenceon the distance between the controlling mirror and the cylinder blockwhich is known as for instance in" Patent "No. 1,924,629.

The force Pr must now be so applied to the cylinder block I that itbalances the resulting moment of the two forces Pk and P5. This meansthat in the illustrated embodiment the lever arm Thus between the sizeof the lever arm 0 and that of the lever arm b; because c should notsurpass the usual dimensions of the cylinder block I. On the other handit is desirable to keep the radius b as small as possible in order togive: a circular form to the controlling opening H, which isadvantageous from the aspect of technical construction, keeping in mindat the same time the -necessary flow cross-section and a sufficient disaforce Prand the lever arm e.

tance from the controlling opening of the neighi-boringcylinder. bore.In case of a plane controlling' mirror one must dispense with thementioned circular form and give the controlling .opening I! the form tobe seen in Fig. 3 due to the relation of the lever arms b and c to oneanother.

'"The'difficulties arising due to this may easily be removed by using aspherical shaped controlling mirror according to Fig. 2, because theexplained force-relation is more favourable. Retaining the moment'Pk-a,the moment Ps-bi may be made essentially smaller in case of-"the sameforcePs. The torque resulting from these two moments on the cylinderblock; which-is-eifec- L tive around the ball I3, is compensatedin'caseof suitable-ball radius by-a'moment resulting from The force P1results from the forces of the spherically constructed controllingmirror. As formerly, aresulting force Pr on the controllingsurface'remains. As the moments, as proved above, are balanced withoutthe help of the fOICPry-thiS force 'Pr' may now become effective in theaxis 2 of-the cylinder-block. Therefore, it doesnotnecessitate a specialequilibrium chamber of greater-diameter, this being also advantageous"with respect to the friction losses.

The force Pr compensates foranyunbalance between PS and Pk, whichexplains the function of the relief chamber'l'fla.

Regarding the manufacture, it'is'further essential in this connectionthat the controlling openings ll'may be vertical to thecontrollingmirror in spite of their inclined position inthe cylinder 5;block.

The ball'form of the controlling mirror 'also 'results in a'decrease ofthe diameterd-ofthecontact surface of the cylinder "bloclethisbeingnotonly favourable with respect to the friction-losses, but also has theadvantage that'the'cylinder bores may lead through the'entirelengthofthe cylinder block in order to close'them afterwards bymeans of a stop20 or the'like. 'Th'ese lleoutside of the controlling mirrorsurface'and, therefore, cannot influence its-quality.

It maybe pointed out'thatthe'transmission device according to theembodiments shown and described operates without the usual Card'anjoint, because 'the'piston rods themselves-serve asmoment transmittingmember 'forthe cylinder block or the driving disc or flange.-Forthispurof the piston type, comprising, in combination, a cylinderblock formed with a plurality of cylinder bores approximately parallelto the axis of said block, each of said cylinder bores being providedwith and communicating with a respective controlling orifice in the endface of said block and said end face being spherical; means forsupporting said block for rotation about its axis, said means having aspherical controlling surface cooperating with said controlling orificesin said spherical end face and supporting only said end face of saidblock; a driving flange mounted for rotation about an axis which latteris inclined to the axis of rotation of said cylinder block; a centeringjoint for concentrically guiding said driving flange and said cylinderblock with respect to one another, the center of said joint coincidingwith the driving plane of said driving flange; pistons in said cylinderbores; a piston rod for each of said pistons operatively connected tosaid driving flange and to its respective piston, said piston rodstransmitting the driving movement between the cylinder block and thedriving flange by engaging their respective pistons; and an equilibriumchamber for hydraulically relieving the controlling surfaces, saidchamber being centrically arranged so as to relieve said surfaceswithout creating any turning moment.

HANS MOLLY.

REFERENCES CITED The following references are of record in the

